Changes in collagen fibril network organization and proteoglycan distribution in equine articular cartilage during maturation and growth

Abstract

The aim of this study was to record growth-related changes in collagen network organization and proteoglycan distribution in intermittently peak-loaded and continuously lower-level-loaded articular cartilage. Cartilage from the proximal phalangeal bone of the equine metacarpophalangeal joint at birth, at 5, 11 and 18 months, and at 6-10 years of age was collected from two sites. Site 1, at the joint margin, is unloaded at slow gaits but is subjected to high-intensity loading during athletic activity; site 2 is a continuously but less intensively loaded site in the centre of the joint. The degree of collagen parallelism was determined with quantitative polarized light microscopy and the parallelism index for collagen fibrils was computed from the cartilage surface to the osteochondral junction. Concurrent changes in the proteoglycan distribution were quantified with digital densitometry. We found that the parallelism index increased significantly with age (up to 90%). At birth, site 2 exhibited a more organized collagen network than site 1. In adult horses this situation was reversed. The superficial and intermediate zones exhibited the greatest reorganization of collagen. Site 1 had a higher proteoglycan content than site 2 at birth but here too the situation was reversed in adult horses. We conclude that large changes in joint loading during growth and maturation in the period from birth to adulthood profoundly affect the architecture of the collagen network in equine cartilage. In addition, the distribution and content of proteoglycans are modified significantly by altered joint use. Intermittent peak-loading with shear seems to induce higher collagen parallelism and a lower proteoglycan content in cartilage than more constant weightbearing. Therefore, we hypothesize that the formation of mature articular cartilage with a highly parallel collagen network and relatively low proteoglycan content in the peak-loaded area of a joint is needed to withstand intermittent stress and shear, whereas a constantly weight-bearing joint area benefits from lower collagen parallelism and a higher proteoglycan content.

Minor Influence of Lifelong Voluntary Exercise on Composition, Structure, and Incidence of Osteoarthritis in Tibial Articular Cartilage of Mice Compared with Major Effects Caused by Growth, Maturation, and Aging

“…Joint loading affects the content and distribution of PGs [7,16,26,27,52]. However, we did not observe any differences in the content or distribution of PGs between the sedentary controls and runners ( Figure 2).…”

“…The composition and structure of AC is modified during growth and maturation due to remodeling of the AC matrix [2][3][4][5]. It has been reported that the cartilage remodeling is affected by external loading of the joints [6][7][8]. Remodeling can be considered an adaptation to joint loading conditions and demands, as it is known that the composition and structure of AC modulates the mechanical properties and thereby the function of AC [9][10][11][12].…”

Cartilage canals in the distal intermediate ridge of the tibia of fetuses and foals are surrounded by different types of collagen

“…; Hyttinen et al. ). It is not known how long it takes for the collagen type I/eosinophilic ring to become visible in histological section after induction of collagen production from the appropriate cell.…”

Musculoskeletal Pathology

“…10 At the ossification front, there is an abrupt change in biomechanical strength, and the arterioles that traverse this zone are particularly vulnerable to insult. 13,14 In osteochondrosis, biomechanical loading is thought to result in focal microvascular changes that lead to ischemia, retention of cartilage cores, and subsequent chondronecrosis. Mechanical dissection of the lesion results in an osteochondral flap, which may detach and become a free-floating fragment within the joint.…”